SDN/SDDC Retreat in Miami, Florida (November 4th-6th)
Separate SDN hype from real life!

Configuring lines and terminals

Numerous comments to the "terminal exec prompt" post told me that it might be good to review the line/terminal configuration rules:

  • If you want to configure a permanent line characteristic (for example, international), you should do so in the VTY configuration (see also how the VTY configurations are merged);
  • If you want a temporary change in the characteristic of your current line (VTY or console), use terminal characteristic to enable it or terminal no characteristic to disable it.

For example, IOS performs DNS lookups on all names entered by a user (assuming the ip domain-lookup is not disabled). You can change that behavior with the domain-lookup characteristic (enabled by default). To permanently disable DNS lookups on all VTYs use:

line vty 0 4
no domain-lookup
To disable the lookup for the current session, use terminal no domain-lookup.

1 comment:

  1. It is handy to have domain lookup feature but annoying to wait for the domain lookup for the wrong command. The fix is simple, change the transport preference to none in the vty/console line. The drawback, you wil have to use a specific telnet/ssh command infront before typing the ip address if you want to connect to another device. (eg. "telnet w.x.y.z" instead of simply typing "w.x.y.z" to login to another device).

    ip domain-lookup
    ip name-server w.x.y.z
    line vty 0 15
    transport prefer none
    logging synchronous
    line con 0
    transport prefer none
    logging synchronous


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Ivan Pepelnjak, CCIE#1354 Emeritus, is an independent network architect. He has been designing and implementing large-scale data communications networks as well as teaching and writing books about advanced technologies since 1990. See his full profile, contact him or follow @ioshints on Twitter.